Effective delivery of an active pharmaceutical ingredient is challenging. Hydrophobic active ingredients present challenges associated with poor aqueous solubility and slow dissolution rate while hydrophilic active ingredients, though readily soluble in aqueous environments, are poorly absorbed due to membrane impermeability and/or enzymatic degradation. While separately they present a formidable challenge, delivering both in a single device is exponentially more difficult. A multitude of drug delivery devices attempting to address these challenges and provide for release of pharmaceutically active ingredients in a controlled and continuous rate for a prolonged period of time have been described.
For example, vaginal ring technologies have been described providing for a once-a-month, or once-every-three to twelve month dosing regimen. Existing vaginal ring systems are typically manufactured from silicone elastomers and/or ethylene vinyl acetate polymers. See, for example, U.S. Pat. No. 4,016,251. Release from vaginal rings is generally controlled by diffusion of the active pharmaceutical ingredient and/or erosion of the ring matrix. Manufacture of existing vaginal ring systems is fairly complex as existing rings comprise an inner reservoir or core containing the active pharmaceutical ingredient and an outer silicone elastomer or ethylene vinyl acetate polymer shell. Further, in existing rings diffusion from the core to the shell reduces the overall rate of diffusion so that extended metered release into the vaginal lumen is obtained. However, cores and shells that are amenable to passage of hydrophobic compounds are not typically amenable to passage of hydrophilic compounds. Hence, delivery of dissimilar molecules with existing ring technologies is challenging.
Accordingly, there are a number of areas in which current vaginal ring technology as well as other drug delivery devices can be improved. These include manufacturing ease, cost, multi-drug delivery, and environmental impact.